As a method for sterilizing food containers (for example, bottles), known from the past is a method wherein hot water is injected into the interior of the food containers or a method wherein the containers are sterilized with a sterilant of peracetic acid series. The techniques disclosed in patent literatures 1 and 2 proposed by the present inventors are examples of the art thereof.
The patent literature 1 relates to a method wherein food containers are initially brought into contact with hot water above 63° C. to effect sterilization of bacteria of Penicillium which are sterilized only with hot water and thereafter spore-forming bacteria capable of forming spores such as bacteria of Bacillus as well as fungi having ascospores such as Neosartorya which are unable to be sterilized only with hot water are sterilized with a sterilant comprising an aqueous solution of peracetic acid, so as to sterilize food containers effectively without using hot water and the sterilant of peracetic acid series in an amount more than the necessary amount.
The patent literature 2 relates to a method wherein a sterilant of peracetic acid series containing peracetic acid at a concentration of 1000˜1500 ppm together with hydrogen peroxide is heated at 60° C. or higher and is injected by the aid of a nozzle into at least the interior of a PET bottle to effect sterilization of the PET bottle.
In sterilization of containers with a sterilant of peracetic acid series, there is either an uneconomical factor in prolonging the sterilizing time for achieving sufficient sterilization or a requisite that the concentration of the sterilant of peracetic acid series is to be decreased for satisfactorily washing the sterilized containers with sterile water after sterilization. Hence, a beneficial way has hitherto been required for conducting sterilization with the sterilant of peracetic acid series having a low concentration within a short period of time. The patent literature 2 is evaluated as a technique capable of solving such problems.    [Patent Literature 1] Japanese Patent No. 3,201,133    [Patent Literature 2] Japanese Patent No. 3,080,347
As a result of continuing extensive research by tracing the aforesaid inventions to develop economical containers and accessories offered for aseptic filling and being capable of exhibiting a sterilizing effect within a short period of time and to develop a sterilization method for the interior of sterilizing apparatus for aseptic filling, it has been discovered surprisingly by the present inventors that a sterilization method exhibiting an extremely high sterilizing effect can be established by mixing hydrogen peroxide with peracetic acid at a concentration lower than the concentration of the peracetic acid and maintaining the concentration of peracetic acid at 500-3000 ppm, nevertheless it is a common sense in a sterilant of peracetic acid series comprising peracetic acid incorporated with hydrogen peroxide that the proportion of hydrogen peroxide is hitherto greater, i.e. a ratio of hydrogen peroxide/peracetic acid being at least 1. The present invention has been accomplished on the basis of the above finding.